Method for selecting a satellite

ABSTRACT

The invention relates to a method for selecting a satellite which is designed to send a global navigation satellite system-signal, also known as a GNSS-Signal, to a vehicle, consisting of: measuring measurement position data of the vehicle in relation to the satellite based on the GNSS-Signal; determining redundant reference position data of the vehicle in relation to the measurement position data determined according to the GNSS-Signal; and selecting the satellite when a comparison of the measurement position data and the reference position data meets a predetermined condition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/344,440, filed Jul. 31, 2014, which claimed priority to GermanApplication Nos. 10 2011 082 534.7, filed Sep. 12, 2011, 10 2011 082539.8, filed Sep. 12, 2011, 10 2011 086 710.4, filed Nov. 21, 2011, 102012 207 297.7, filed May 2, 2012, and International Application No.PCT/EP2012/067866, filed Sep. 12, 2012, all of which are hereinincorporated by reference in their entirety.

FIELD OF THE INVENTION

The invention relates to a method for selecting a satellite that isdesigned to send a GNSS signal to a vehicle, a control apparatus forperforming the method and a vehicle having the control apparatus.

BACKGROUND OF THE INVENTION

WO 2011/098333 A1 discloses the practice of using different sensorvariables in a vehicle in order to improve already existent sensorvariables or to generate new sensor variables and hence to enhance therecordable information.

It is an object to improve the use of a plurality of sensor variablesfor enhancing information.

SUMMARY AND INTRODUCTORY DESCRIPTION OF THE INVENTION

The object is achieved by the technical features disclosed herein and byway of the method disclosed herein.

According to one aspect of the invention, a method for selecting asatellite that is designed to send a global navigation satellite systemsignal, called a GNSS signal below, to a vehicle comprises the steps of:

measurement of measurement location data for the vehicle with respect tothe satellite on the basis of the GNSS signal,

determination of reference location data for the vehicle that areredundant relative to the measurement location data determined on thebasis of the GNSS signal; and

selection of the satellite when juxtaposition of the measurementlocation data and the reference location data satisfies a predeterminedcondition.

The specified method is based on the consideration that positioninformation for the vehicle could be derived from the GNSS signal. Onthe basis of this consideration, however, the specified method involvesrecognizing that the GNSS signal could, prior to being received at thevehicle, pass through different sources of interference that could addnoise to the GNSS signal, as a result of which it no longer indicatesthe true position of the vehicle. Such sources of interference could bemultipath reception, shadowing or reflections.

On the basis of these considerations, it is a concept of the specifiedmethod to stipulate for the GNSS signal an expected value from which areference for the quality of the GNSS signal can be derived withsufficient precision. If the deviation between the GNSS signal and theexpected value used as a reference is sufficiently small, the satelliteis selected as a source for the GNSS signal.

In one development, the juxtaposition of the measurement location dataand the reference location data involves a difference being formedbetween the measurement location data and the reference location data.This development is based on the consideration that although thejuxtaposition could be performed on the basis of any desired filter, thedifference between the two location data immediately reveals thedeviation therein relative to one another, which provides a statisticaldescription of the GNSS signal and hence immediately permits the qualitythereof to be assessed.

In this regard, it may be preferred for a predetermined condition thatis permitted to be a maximum admissible error between the measurementlocation data and the reference location data that is in turn a qualitycontrol for the selection of the satellite.

With particular preference, the maximum admissible error may bedependent on a standard deviation that is calculated on the basis of asum comprising a reference variance for the reference location data anda measurement variance for the measurement location data. Thisdevelopment is based on the consideration that in this case twostatistical values are simultaneously used for the selection of thesatellite. The reference value could be determined iteratively, with thequality thereof becoming ever higher with ascending iteration steps.However, this means that the reference value may itself have a highlevel of noise and contain errors at first, which is why it would not beexpedient at this time to select a GNSS signal with a very high quality.Since the maximum admissible error and hence the admissible deviationare chosen on the basis of the variances and hence the noise in the twolocation data, the maximum admissible error between the location dataand the noise in the location data themselves are correlated for theselection. This ensures that the noise from the satellite to be selectedmatches the deviation between the expected value and the measured valuerepresented by the GNSS signal.

In an additional development of the specified method, the maximumadmissible error corresponds to a multiple of the standard deviationsuch that a probability that the measurement location data are below apredetermined threshold value in a scatter range that is dependent onthe standard deviation. This ensures that the inevitable scatter in thedeviations between the reference location data, that is to say theexpected value, and the measured location data, that is to say themeasured value, does not select a satellite that is actually suitable ona nonrandom basis.

According to a further aspect of the specified invention, a method forselecting a satellite that is designed to send a global navigationsatellite system signal, called a GNSS signal below, to a vehiclecomprises the steps of:

measurement of measurement location data for the vehicle with respect tothe satellite on the basis of the GNSS signal,

selection of the satellite when the measurement location data satisfy apredetermined condition.

The specified method is based on the consideration that the satellitecould be selected just using hard decision bases, because the vehiclethat uses the GNSS signal is subject to particular physical constraints.By way of example, the vehicle must not accelerate arbitrarily and isalso unable to travel at an arbitrary speed. These physical constraintscan be used as a basis for selecting the satellite without the need forfurther comparison measurements in order to check the quality of theGNSS signal.

Therefore, the predetermined condition may preferably be a physicalconstraint to which the vehicle is subject.

With particular preference, the physical constraint may be a limitacceleration and/or a limit speed for the vehicle.

In one particular development of the specified method, the measurementlocation data may comprise a speed and/or an acceleration, for example,that is derived from the GNSS signal. In this way, it is possible tocheck directly whether or not the aforementioned physical constraintsare satisfied.

According to a further aspect of the specified invention, a method forselecting a satellite that is designed to send a global navigationsatellite system signal, called a GNSS signal below, to a vehiclecomprises the steps of:

recording of a location for at least three satellites among one another,said satellites comprising the satellites to be selected;

measurement of measurement location data for the vehicle with respect tothe satellite on the basis of the GNSS signal from the satellite to beselected,

selection of the satellite to be selected on the basis of juxtapositionof the location of the three satellites relative to one another and themeasurement location data.

The specified method is based on the consideration that the threesatellites with the satellite to be selected may have an inherentlyknown location relative to one another. On the basis of this knownlocation, the vehicle must also move in a manner that is to be expectedwith respect to these three satellites. This movement that is to beexpected can be used as a decision basis for selecting the GNSS signaland hence the satellite to be selected.

In this case, the specified method involves recognizing that thelocation of the three satellites relative to one another comprisesrelative position statements. In order for a GNSS signal to beincorrectly interpreted as error-free, the GNSS signals from all threeGNSS satellites would need to be corrupted in an exactly identicalmanner by shadowing, multiple reflections, and so on, which is as goodas ruled out on account of the totally different signal propagationpaths, however. Therefore, the specified method delivers a very reliabledecision basis for the selection of a satellite.

In one development of the specified method, the juxtaposition of thelocation of the three satellites relative to one another and themeasurement location data comprises juxtaposition of the distances ofthe vehicle relative to the three satellites. This development is basedon the consideration that the GNSS signals from the three satellitescould be examined for any inconsistencies on the basis of the locationof the satellites relative to one another. If all three satellites arein front of the vehicle from the point of view of the direction oftravel of the vehicle, for example, then all three distances must beshorter. In addition, from trigonometric perspectives, it is possible todetermine how quickly individual distances from the vehicle to therelevant satellite can become shorter. The distances of the satellitesrelative to one another can be derived from information transmitted bythe satellites.

According to a further aspect of the specified invention, a method forselecting a satellite that is designed to send a global navigationsatellite system signal, called a GNSS signal below, to a vehiclecomprises the steps of:

recording of a distance for the vehicle relative to the satellite and ofa relative speed for the vehicle relative to the satellite in the visualdirection of the satellite from the GNSS signal;

selection of the satellite on the basis of juxtaposition of the recordeddistance and the recorded relative speed.

The specified method is based on the consideration that the distancefrom the vehicle to the satellite and the relative speed of the vehiclewith respect to the satellite are dependent on one another, that is tosay correlated. In addition, the specified method is based on theconsideration that the relative speed could be recorded from the GNSSsignal, for example on the basis of Doppler effects, while the distancefrom the vehicle to the satellite could be recorded on the basis of apropagation time of the GNSS signal, for example, and henceindependently of the measurement for recording the relative speed. Theconcept of the specified method is thus that it is neverthelessnecessary for both measurements to match, that the measured variables tobe recorded, that is to say the relative speed and the distance, aredependent on one another.

The juxtaposition can be effected arbitrarily on the basis of differenceformation or other filtering. Difference formation immediately revealsthe decision basis for selection of the satellite with minimumcomputation time.

For all methods specified above, the following developments can also beimplemented:

The measurement location data for the vehicle and the reference locationdata for the vehicle may each comprise a distance from the satelliteand/or a relative speed in the visual direction of the satellite. Thatis to say that the method specified according to the last aspect of theinvention selects the satellite on the basis of an analysis of themeasurement location data in themselves, this making use of theadvantage that the GNSS signal transmits the measurement location datausing principles that can be recorded by measurement in two differentways.

In a preferred development of one of the specified methods, the distancefrom the satellite and/or the relative speed in the visual direction ofthe satellite can be ascertained as appropriate from a code measurementand a phase measurement for the GNSS signal.

The GNSS signal used may be a global positioning system signal, GPSsignal for short, a

signal, GLONASS signal for short, or a Galileo signal, for example.Hence, an alternative or additional comparison variable for the vehiclelongitudinal speed would be available, on the basis of which theinformation content of the tire radius to be recorded could be improved.By way of example, the GNSS signal allows network subscribers in anonboard network on the vehicle, such as sensors, to have their timingsynchronized with a correspondingly high level of precision on accountof the high-precision timestamp of said signal. Such synchronization iscurrently the focus of current development pertaining to Car2Xcommunication, that is to say data interchange from a vehicle to othervehicles or systems in the surroundings, such as traffic lights or otherinfrastructure components. The interchange of information aboutaccidents and other hazard locations, about the condition of the road,road signs and much more makes it possible to attain an increase insafety and convenience. In many cases, this needs to involve theinformation being provided in real time. in order to ensure this realtime, the information can be provided with a high-precision timestamp,for example, which is linked to the information by the respectivenetwork subscriber. This timestamp needs to have a correspondingly highlevel of precision, however, which is ensured by the selection of anuncorrupted GNSS signal.

In another development of one of the specified methods, the referencelocation data are dependent on driving dynamics data and/or odometrydata for the vehicle. This development is based on the considerationthat the reference location data can be defined more precisely on thebasis of the GNSS signal, for example in a fusion filter. This could beaccomplished by juxtaposing the reference location data with the GNSSsignal itself or location data derived from the GNSS signal, like themeasurement location data, in an observer, for example. Such an observermay include any filter that permits analog or digital state observationof the vehicle. It is thus possible to use a Luenberger observer, forexample. If the noise also needs to be taken into account, a Kalmanfilter would be suitable. If the shape of the noise also needs to betaken into account, it would be possible, if need be, to use a particlefilter, which has a basic set of available noise scenarios and selectsthe noise scenario that is to be taken into account for the eliminationusing a Monte Carlo simulation, for example. The observer is preferablya Kalman filter, which provides an optimum result in respect of thecomputation resources that it requires. The observation makes thereference location data ever more precise over time and said datatherefore also allow ever more precise GNSS signals to be selected.

According to a further aspect of the invention, a control apparatus isset up to perform one of the specified methods.

In one development of the specified control apparatus, the specifiedapparatus has a memory and a processor. In this case, a specified methodis stored in the memory in the form of a computer program, and theprocessor is provided for the purpose of executing the method when thecomputer program is loaded from the memory into the processor.

According to a further aspect of the invention, a computer programcomprises program code means in order to perform all the steps of one ofthe specified methods when the computer program is executed on acomputer or one of the specified apparatuses.

According to a further aspect of the invention, a computer programproduct contains a program code that is stored on a computer-readabledata storage medium and that, when executed on a data processing device,performs one of the specified methods.

According to a further aspect of the invention, a vehicle comprises aspecified control apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

The properties, features and advantages of this invention that aredescribed above and also the manner in which these are achieved becomemore clearly and more distinctly comprehensible in connection with thedescription below of the exemplary embodiments, which are explained inmore detail in connection with the figures, in which:

FIG. 1 shows a basic illustration of a vehicle with a fusion sensor,

FIG. 2 shows a basic illustration of the fusion sensor from FIG. 1, and

FIG. 3 shows a schematic illustration of a vehicle receiving a GNSSsignal.

DETAILED DESCRIPTION OF THE INVENTION

In the figures, technical elements that are the same are provided withthe same reference symbols and are described only once.

Reference is made to FIG. 1, which shows a basic illustration of avehicle 2 with a fusion sensor 4.

In the present embodiment, the fusion sensor 4 uses an inherently knownGNSS receiver 6 to receive location data 8 for the vehicle 2, which datacomprise an absolute position for the vehicle 2 on a road 10. Besidesthe absolute position, the location data 8 from the GNSS receiver 6 alsocomprise a speed for the vehicle 2. In the present embodiment, thelocation data 8 from the GNSS receiver 6 are derived—in a manner that isknown to a person skilled in the art—in the GNSS receiver 6 from a GNSSsignal 12 that is received via a GNSS antenna 13 and that is thereforecalled GNSS location data 8 below. For details in this regard, referenceis made to the relevant specialist literature in this regard.

The fusion sensor 4 is designed—in a manner that is yet to bedescribed—to enhance the information content of the GNSS location data 8derived from the GNSS signal 12. This is firstly necessary because theGNSS signal 12 may have a very high signal-to-noise band ratio and maythus be very imprecise. Secondly, the GNSS signal 12 is not alwaysavailable.

In the present embodiment, the vehicle 2 also has an inertial sensor 14that captures driving dynamic data 16 for the vehicle 2. These are knownto include a longitudinal acceleration, a lateral acceleration and alsoa vertical acceleration and a roll rate, a pitch rate and also a yawrate for the vehicle 2. In the present embodiment, these drivingdynamics data 16 are used in order to enhance the information content ofthe GNSS location data 8 and, by way of example, to define the positionand the speed of the vehicle 2 on the road 10 more precisely. The moreprecisely defined location data 18 can then be used by a navigationappliance 20 itself even when the GNSS signal 12 is not available atall, for example in a tunnel.

To further enhance the information content of the GNSS location data 8,the present embodiment may optionally also make use of wheel speedsensors 22 that record the wheel speeds 24 of the individual wheels 26of the vehicle 2.

Reference is made to FIG. 2, which shows a basic illustration of thefusion sensor 4 from FIG. 1.

The fusion sensor 4 receives the measurement data already mentioned inFIG. 1. The fusion sensor 4 is intended to output the more preciselydefined location data 18. The basic concept in this regard is that ofjuxtaposing the information from the GNSS location data 8 with thedriving dynamics data 16 from the inertial sensor 14 into a filter 30and thus increasing a signal-to-noise band ratio in the location data 8from the GNSS receiver 6 or the driving dynamics data 16 from theinertial sensor 14. To this end, although the filter may be in any form,a Kalman filter achieves this object most effectively with comparativelylow computational resource requirement. Therefore, the filter 30 belowwill preferably be a Kalman filter 30.

The Kalman filter 30 receives the more precisely defined location data18 for the vehicle 2 and comparison location data 34 for the vehicle 2.In the present embodiment, the more precisely defined location data 18are generated from the driving dynamics data 16 using a strapdownalgorithm 36, which is known from DE 10 2006 029 148 A1, for example.Said data contain more precisely defined position information about thevehicle, but also other location data about the vehicle 2, such as thespeed thereof, the acceleration thereof and the heading thereof. Bycontrast, the comparison location data 34 are obtained from a model 38of the vehicle 2 that is first of all fed with the GNSS location data 8from the GNSS receiver 6. These GNSS location data 8 are then used inthe model 38 to determine the comparison location data 34, which containthe same information as the more precisely defined location data 18. Themore precisely defined location data 18 and the comparison location data34 differ only in terms of their values.

The Kalman filter 30 takes the more precisely defined location data 18in the comparison location data 34 as a basis for calculating an errorbudget 40 for the more precisely defined location data 18 and an errorbudget 42 for the comparison location data 34. An error budget isintended to be understood below to mean a total error in a signal, whichis made up of various individual errors during the recording andtransmission of the signal. In the case of the GNSS signal 12 and hencein the case of the GNSS location data 8, a corresponding error budgetmay be made up of errors in the satellite orbit, in the satellite clock,in the residual refraction effects and of errors in the GNSS receiver 6.

The error budget 40 for the more precisely defined location data 18 andthe error budget 42 for the comparison location data 34 are thensupplied as appropriate to the strapdown algorithm 36 and to the model38 for the purpose of correcting the more precisely defined locationdata 18 or the comparison location data 34. This means that the moreprecisely defined location data 18 and the comparison location data 34are iteratively purged of their errors.

In the present development, the GNSS receiver 6 receives the GNSS signal12 from a GNSS satellite 44 that is shown in FIG. 3. The GNSS signal 12sent by this GNSS satellite 44 may be subject to a greater or lesserlevel of noise, for which reason the model 38 in the present embodimentis extended by a function that evaluates the GNSS signal 12 itself orthe GNSS location data 8 derived on the basis of the GNSS signal 12 andthen selects the GNSS satellite 44 as source for the GNSS signal 12 onthe basis of the evaluation.

The methods below, illustrated with reference to FIG. 3, can be combinedwith one another as desired, even if they are described individually bythemselves. It is thus not necessary to perform just one of the methodsfor selecting a satellite. The order is also not important initially.

Reference is made to FIG. 3, which shows a first schematic illustrationof a vehicle 2 receiving the GNSS signal 12.

The vehicle 2 is moving over the road 10 at a speed 46 and anacceleration 48. In this case, it is intended to be assumed that thevehicle 2 is slowing down, as a result of which the speed 46 and theacceleration 48 are opposite. The speed 46 and the acceleration 48 canbe determined from the GNSS signal 12.

This can be accomplished by differentiated carrier phase measurement forthe GNSS signal 12, for example. This involves taking into account analteration in the carrier phase of the GNSS signal 12 over time, saidalteration being obtained on the basis of the Doppler effect caused bythe moving vehicle 2. The result obtained for the differentiated phasemeasurement is a visual direction speed 50, which can be converted intothe speed 46 and the acceleration 48 in a manner that is known to aperson skilled in the art.

Alternatively or in addition, it is also possible to take into accountthe position of the vehicle on the basis of a code measurement, fromwhich a distance 52 between vehicle 2 and the satellite 44 is detectedby means of propagation time detection for the GNSS signal 12, fromwhich distance the speed 46 and the acceleration 48 can be calculatedlikewise in a manner that is known to a person skilled in the art.

The first of the four methods is described below:

The core concept of the first method is that the speed 46 and theacceleration 48 must satisfy certain physical constraints that cannot beinfringed. An ordinary automobile that is not designed for sportydriving will not travel faster than 300 km/h. In addition, it cannot beslowed down at more than 1.2 times acceleration due to gravity. If theGNSS signal 12 yields values that infringe this constraint, thesatellite 44 can be eliminated or can be ignored as a source ofinformation for the GNSS location data 8, as appropriate.

The second method is described below:

The second method is based on the consideration that a visual speed 50,that is to say the movement of the vehicle in the direction of thesatellite, and a distance 52 to the satellite 44 can be recordeddirectly from the GNSS signal 12. The visual speed 50 and the distance52 can be reconstructed on the basis of the more precisely definedlocation data 18 using alternative measurement principles, which meansthat the visual speed and distance to the satellite 44 that are derivedfrom the GNSS signal 12 can be regarded as expected values for thevisual speed 50 and the distance 52 that are transmitted with the GNSSsignal 12.

The core concept of the second method is thus that deviations betweenthe expected values and the corresponding information from the GNSSsignal 12 must correspond to the total noise, that is to say that adeviation that can be calculated using the total noise corresponds tothe aforementioned actual deviation.

This concept will be described below in a nonrestrictive manner withreference to a comparison of the visual speed 50 obtained from the GNSSsignal 12. The second method can alternatively or additionally beperformed in the same manner on the basis of the distance 52 to thesatellite 44.

The measured noise σ_(GNSS) for the visual speed 50 from the GNSS signaland an uncertainty about the more precisely defined location data 18 andalso the uncertainty of all other measurement data used in thereconstructed visual speed 50 and hence the measured noise σ_(rec) forthe expected value add up to form a total measured noiseσ_(meas)=σ_(GNSS)+σ_(rec). In addition, a deviation μ can be determinedbetween the visual speed 50 and the reconstructed visual speed, that isto say the expected value. For the selection of the satellite, athreshold is now stipulated for the extent to which a standard normaldeviation obtained from the total measured noise:μ_(stan)=√{square root over (σ_(GNSS)+σ_(rec))}deviates from the deviation μ in the expected value, that is to say thereconstructed visual speed relative to the visual speed 50 measured fromthe GNSS signal 12.

This ensures that the precision of the measured values 50, 52transmitted with the GNSS signal 12 is matched to the precision of theexpected value, that is to say the reconstructed visual speed and/or thereconstructed distance to the satellite from the more precisely definedlocation data 18 from the fusion sensor 4.

So that the specified method does not eliminate too many satellites 44,the threshold used for the deviation μ may be a multiple of the standarddeviation μ_(stand), the multiple being able to be oriented to thedesired spread for the selection.

The third method is described below.

The basic concept of the fourth method is to be able to determine thelocation of the satellite 44 and the further satellites 54, 56 relativeto one another and from the point of view of the vehicle independentlyof the visual speed 50 and the distance 52, that is to say usinginformation that is transmitted with the GNSS signal 12, for example.

When the location of the satellites 44, 54, 56 relative to one anotheris known, the visual speed 50 and the distance 52 to the individualsatellites 44, 54, 56 cannot change arbitrarily. If all satellites arein front of the vehicle 2 in the direction of travel 46, for example,then all distances 52 to the individual satellites 44, 54, 56 mustbecome correspondingly shorter.

In practice, this can be performed using a trigonometric comparison, forexample. If the distances 58 of the satellites from one another areknown, and the distances from the vehicle 2 to at least two of thesatellites 54, 56, then the distance 52 is overdetermined, since it canbe reconstructed from the prior information. Nevertheless, thereconstructed distance must correspond to the actual distance 52, andthe quality of the GNSS signal 12 from the satellite 44 can then beassumed to be sufficient for the fusion sensor 4.

Ultimately, an overdetermined equation system that needs to be able tobe resolved consistently can be set up from the total distances 58between the satellites 44, 54, 56 and the measured distances 52 or thevisual speeds 50 of the vehicle 2 relative to the satellites 44, 54, 56mathematically using known trigonometric dependencies of the satellites44, 54, 56 and the vehicle 2 relative to one another. An advantage ofthis equation system is that the inconsistency can be located and hencecan be attributed to a particular satellite 44, 54, 56, as a result ofwhich the relevant satellite 44, 54, 56 and hence the GNSS signal 12therefrom can be eliminated.

Within the framework of the fourth method, it is a basic concept thatthe visual direction speed 50 and the distance 52 between the vehicle 2and the satellite 44 are recorded using different measurement methods(carrier phase measurement and code measurement). They nevertheless needto correspond to one another. That is to say that if the distance 52 isderived on the basis of time, the visual direction speed 50 must beobtained. Otherwise, there is an error that can be taken as a basis foreliminating the satellite 44.

Preferably, the methods for selecting the satellite 44 are performed inthe specified order, since firstly the precision checked by thespecified methods and secondly the for performing the specified methodincrease from the first to the fourth method. It is thereforeinconvenient from the point of view of computation to include satellitesthat are totally implausible on the basis of the physical constraints,which satellites can already be eliminated using the first method, inthe equation system of the third method.

While the above description constitutes the preferred embodiment of thepresent invention, it will be appreciated that the invention issusceptible to modification, variation, and change without departingfrom the proper scope and fair meaning of the accompanying claims.

The invention claimed is:
 1. A method for selecting a satellite that isdesigned to send a global navigation satellite system (“GNSS”) signal toa vehicle, the method comprising: measuring, at a control apparatus of avehicle, measurement location data for the vehicle with respect to thesatellite on the basis of the GNSS signal received at a GNSS receiver ofthe vehicle, wherein the measurement location data includes a speed ofthe vehicle or an acceleration of the vehicle; determining, at thecontrol apparatus, if a predetermined condition is satisfied bycomparing the speed of the vehicle or the acceleration of the vehiclemeasured on the basis of the GNSS signal to a speed or an accelerationof the vehicle determined differently from the measurement location datafor the vehicle determined on the basis of the GNSS signal; selecting,at the control apparatus, the satellite as a source for the GNSS signalfor the vehicle when the speed of the vehicle or the acceleration of thevehicle measured on the basis of the GNSS signal satisfies thepredetermined condition; determining, at the control apparatus,locations for at least three satellites from a point of view of thevehicle, wherein the at least three satellites have a known locationrelative to one another, said satellites comprising the satellite to beselected; determining, at the control apparatus, a relative distance forthe vehicle relative to the satellite to be selected and a speed of thevehicle relative to the satellite to be selected in the visual directionof the satellite to be selected from the GNSS signal; selecting, at thecontrol apparatus, the satellite as a source for the GNSS signal for thevehicle: when the speed of the vehicle relative to the satellite to beselected in the visual direction of the satellite to be selected fromthe GNSS signal or the acceleration of the vehicle measured on the basisof the GNSS signal satisfies the predetermined condition; and when thelocation of the three satellites relative to one another from a point ofview of the vehicle and the measurement location data correlate; andwhen the determined relative distance and the determined relative speedcorrelate; and eliminating or ignoring, at the control apparatus, atleast one of the at least three satellites as the source for the GNSSsignal for the vehicle when the locations of the three satellitesrelative to one another from the point of view of the vehicle and alocation of the at least one of the at least three satellites derivedfrom the measurement location data do not correlate.